The operation of electronically timed detonators, also known as electronic delay detonators, or EDDs, for blasting, mining, quarrying and similar operations is conventionally performed by use of a network or harness of wires that connect all the detonators together and to the devices that control them. Typically, each detonator is located below ground in the bulk of the explosive material, with a connection made to the aforesaid harness at the top of the hole which contains the explosive.
This surface harness wire network has to be connected together and the detonators connected to it. This process causes significant labour costs and generates many of the faults that occur due to failed or damaged connections. Moreover, the wire itself becomes a nuisance. Firstly it prevents easy movement of men and vehicles over the blasting site and is itself easily damaged. Secondly it has to be gathered for disposal being unfit for reuse or it becomes an undesirable material contaminant of the ore body being extracted.
It is therefore desirable to eliminate the surface wiring for EDDs and control the detonators remotely using some wireless means of communication. EDDs to be effective and safe preferably have two way communication with the controlling device in direct communication with the detonators, also known as the blasting machine. Often, the communication means must therefore provide reliable transfer of messages, from a blasting machine to a large number of EDDs. The physical circumstances, particularly in open cast mining or quarrying, give rise to EDDs being laid out in patterns that can extend several hundreds of metres over somewhat irregular terrain.
Persons of skill in the art recognize the potential of wireless detonator systems for significant improvement in safety at the blast site. By avoiding the use of physical connections (e.g. electrical wires, shock tubes, LEDC, or optical cables) between detonators, and other components at the blast site (e.g. blasting machines) the possibility of improper set-up of the blasting arrangement is reduced. With traditional, “wired” blasting arrangements (wherein the wires can include e.g. electrical wires, shock tubes, LEDC, or optical cables), significant skill and care is required by a blasting operator to establish proper connections between the wires and the components of the blasting arrangement. In addition, significant care is required to ensure that the wires lead from the explosive charge (and associated detonator) to a blasting machine without disruption, snagging, damage or other interference that could prevent proper control and operation of the detonator via the attached blasting machine. Wireless blasting systems offer the hope of circumventing these problems.
Another advantage of wireless blasting systems relates to facilitation of automated establishment of the explosive charges and associated detonators at the blast site. This may include for example automated detonator loading in boreholes, and automated association of a corresponding detonator with each explosive charge. Automated establishment of an array of explosive charges and detonators at a blast site, for example by employing robotic systems, would provide dramatic improvements in blast site safety since blast operators would be able to set up the blasting array from entirely remote locations. However, such systems present formidable technological challenges, many of which remain unresolved. One obstacle to automation is the difficulty of robotic manipulation and handling of detonators at the blast site, particularly where the detonators require tieing-in or other forms of hook up to electrical wires, shock tubes or the like. Wireless detonators and corresponding wireless detonator systems may help to circumvent such difficulties, and are clearly more amenable to application with automated mining operations. In addition, manual set up and tieing in of detonators via physical connections is very labour intensive, requiring significant time of blast operator time. In contrast, automated blasting systems are significantly less labour intensive, since much of the set procedure involves robotic systems rather than blast operator's time.
Progress has been made in the development wireless detonator assemblies, and wireless blasting systems that are suitable for use in mining operations, including detonators and systems that are amenable to automated set-up at the blast site. Nonetheless, existing wireless blasting systems still present significant safety concerns, and improvements are required if wireless systems are to become a viable alternative to traditional “wired” blasting systems.